They are correct on Drag not being gender identity, though there are gender variant people who do drag. As far as the crossdresser thing, it?s a semantics issue. Many within the LGBT community will say that if you?re NOT doing it for sexual pleasure, that makes you trans. Just because you don?t want to transition doesn?t make you not trans. There are LOTS of trans folks who have no desire to modify their bodies surgically or hormonally.
So it?s more that the LGBTQ community uses a wider definition of trans, and a narrower definition of ?crossdresser?. I?ve mentioned this a few times on these forums.